Field of the Invention
The invention relates to a switching device including a fixed and a moving contact point and an arc extinguishing device having an arcing chamber surrounding the contact points and constructed as a pack of arc splitters stamped out in a U shape, the arc splitters being kept apart at their ends facing away from the contact points and being held together to form a subassembly.
A generic switching device having an arc extinguishing device is disclosed in European Patent EP 0 556 109 B1. In that switching device or protective device, an arc occurs at opening contact points when an electric current is being disconnected. That arc causes wear at the contact points, that is to say burning away of the contacts, and delays the disconnection of the circuit, since the current continues to flow until the arc is extinguished. The electric switching device is equipped with the arc extinguishing device in order to restrict the damage caused by the arc. That includes an arcing chamber, runner plates and diverse components which, inter alia, also fulfill flow-related tasks.
In that case, the arcing chamber is a pack of arc splitters which are stamped out in a U shape, are disposed in parallel and kept apart. Runner plates are disposed at the upper and lower ends of the arcing chamber. The fixed contact point is connected to the upper runner plate.
The above-described arc extinguishing device functions in the following way: when the contact point is opened, an arc occurs between the contact points moving away from each other. That arc is moved outward in the direction of the arcing chamber by electromagnetic forces. In the process, arc root points migrate away from the contact points along the runner plates that are electrically connected to the circuit. Once the arc reaches the arc splitters, it is subdivided into partial arcs and cooled down by the arc splitters. That leads to the partial arcs being extinguished and to the current flow being stopped.
The electromagnetic forces which move the arc away from the contact points toward the arcing chamber become greater with increasing length of the branches and bases of the arc splitters, that is to say with a more pronounced the U shape of the arc splitters. Long bases, in particular in the case of filigree layouts of arc splitters, entail problems in fixing the arc splitters. In that case, it is not possible to rule out the branches or bases or base tips of the arc splitters coming into contact with one another and welding together.